This project is based on the hypothesis that endotoxin (LPS) causes its biological effects, or some of them, by binding to cells and causing membrane perturbations. The systems to be investigated are in vitro effects of LPS on lymphocytes and macrophages. The events leading up to DNA synthesis and immunoglobulin production in LPS stimulated B cells will be investigated. The binding of LPS to B cells, measurements of affinity, specificity of binding, and possible internalization will be tested. For these studies T cells will be used as controls. Membrane alterations including phospholipid turnover, transport and pinocytic activity will be measured. The types of RNA made during mitogenesis and differentiation will also be determined. The production of messenger and ribosomal RNA will be timed in relation to the mitogen stimulus and the onset of Ig production. The stimulating effect of LPS and the reversal of this effect by steroids will be studied using mouse macrophages as the target cell. Activation will be measured by enzyme synthesis and exocytosis.